On Fri, 30 Apr 2021 16:00:46 -0700, Dixit, Ashutosh wrote: > > On Fri, 30 Apr 2021 15:26:09 -0700, Umesh Nerlige Ramappa wrote: > > > > Looks like the engine can be dropped since all timestamps are in sync. I > > just have one more question here. The timestamp itself is 36 bits. Should > > the uapi also report the timestamp width to the user OR should I just > > return the lower 32 bits of the timestamp? > > How would exposing only the lower 32 bits of the timestamp work? It would work I guess but overflow every few seconds. So if the counters are sampled at a low frequency (once every few seconds) it would yield misleading timestamps. > The way to avoid exposing the width would be to expose the timestamp as a > regular 64 bit value. In the kernel engine state, have a variable for the > counter and keep on accumulating that (on each query) to full 64 bits in > spite of the 36 bit HW counter overflow. > > So not exposing the width (or exposing a 64 bit timestamp) is a cleaner > interface but also more work in the kernel. _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
